An observer is moving away from a sound source of frequency 100 Hz. If the obsever is moving with a velocity `49ms^-1` and the speed of sound in air is `330ms^-1`. The observed frequency is

Options

A. 85 Hz
B. 91 Hz
C. 100 Hz
D. 149 Hz

Answer

A

Explanation

Observer is moving away from source then the apparent frequency `n^1=nxx((v-v^0)/v)`
`v=330ms^-1,v_0=49ms^-1,n=100"Hz"`
`n^1=100xx((330-49)/330)`
`n^1=100xx281/330` =85Hz